def _attack_str(ct, lf):
import frequency
lab = frequency.alphabet(lf)
tf = frequency.probability(ct)
maxs = 0
candk = 0
for k in range(len(lf)):
s = _sum_f(tf, lf, lab, k)
if s > maxs:
maxs = s
candk = k
return candk
def _attack_kn_str(ct,
lf,
maxkn=None,
multh=0.01,
minioc=0.01,
mulstep=False,
maxo=5):
import frequency
lab = frequency.alphabet(lf)
if maxkn is None or maxkn > len(ct):
maxkn = len(ct)
candkn = 1
maxioc = 0
for kn in range(2, maxkn + 1):
cioc = _ioc_str_kn(ct, lab, kn, maxo)
if cioc > maxioc and cioc >= minioc:
if kn % candkn != 0 or cioc - maxioc > multh:
maxioc = cioc
candkn = kn
elif mulstep:
maxioc = cioc
return candkn
def decode(pt, k, ab):
import frequency
return _shift_str(pt, -k, frequency.alphabet(ab))
def decode(ct, k, ab):
import frequency
return _shift_str(ct, k, frequency.alphabet(ab), True)